What is Air Trigger in Asus Rog Phone II

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I saw Asus has launched a new flagship phone specially targeted for gaming. Everything is super good about it but I got a new term in it, they mentioned they have Air Triggers in Asus Rog Phone 2 for gaming. What exactly are those air triggers ? Is it some attachment like we buy separately for phones to add new triggers / controller like buttons in phone ?

This is something new, I just checked and they are actually two extra button on side of the phone for playing games. They are similar to L1 and R1 you find in Playstation controllers. But they are not physical regular buttons, rather they are touch buttons. I think they are inspired from the PUBG and other similar games using capacitive touch.